Feedback processing in adolescence: an event-related potential study of age and gender differences.

Adolescence has frequently been characterized as a period of increased risk taking, which may be largely driven by maturational changes in neural areas that process incentives. To investigate age- and gender-related differences in reward processing, we recorded event-related potentials (ERPs) from 80 participants in a gambling game, in which monetary wins and losses were either large or small. We measured two ERP components: the feedback-related negativity (FRN) and the feedback P3 (fP3). The FRN was sensitive to the size of a win in both adult (aged 23-35 years) and adolescent (aged 13-17 years) males, but not in females. Small wins appeared to be less rewarding for males than for females, which may in part explain more approach-driven behavior in males in general. Furthermore, adolescent boys showed both delayed FRNs to high losses and less differentiation in FRN amplitude between wins and losses in comparison to girls. The fP3, which is thought to index the salience of the feedback at a more conscious level than the FRN, was also larger in boys than in girls. Taken together, these results imply that higher levels of risk taking that are commonly reported in adolescent males may be driven both by hypersensitivity to high rewards and insensitivity to punishment or losses.

Newborn infants learn during sleep.

Newborn infants must rapidly adjust their physiology and behavior to the specific demands of the novel postnatal environment. This adaptation depends, at least in part, on the infant's ability to learn from experiences. We report here that infants exhibit learning even while asleep. Bioelectrical activity from face and scalp electrodes was recorded from neonates during an eye movement conditioning procedure in which a tone was followed by a puff of air to the eye. Sleeping newborns rapidly learned the predictive relationship between the tone and the puff. Additionally, in the latter part of training, these infants exhibited a frontally maximum positive EEG slow wave possibly reflecting memory updating. As newborns spend most of their time sleeping, the ability to learn about external stimuli in the postnatal environment during nonawake states may be crucial for rapid adaptation and infant survival. Furthermore, because eyelid conditioning reflects functional cerebellar circuitry, this method potentially offers a unique approach for early identification of infants at risk for a range of developmental disorders including autism and dyslexia.

Mental health stigma and emotional face processing: An ERP study.

This study takes the first step toward developing an event-related potential (ERP) measure of bias toward people with mental illnesses. We recorded participants' EEGs while they viewed happy and angry faces; they were told half of the people in the photos were mentally healthy while the other half had a diagnosis of schizophrenia, which was indicated by the color of the frame around each face. Afterward, participants rated how dangerous each face looked to them. Participants rated faces with the schizophrenia designation as more dangerous than those designated as mentally healthy. There were significant interactions between facial expression and mental health label for both the early N170 and later P3 amplitudes. Angry expressions elicited larger N170s than happy ones, but only for faces with the schizophrenia label. Thus, angry faces with the schizophrenia designation appeared to be particularly salient and automatically grabbed our participants' attention, at least initially. In contrast, happy faces with the schizophrenia label elicited larger P3s than those with the mentally healthy designation. This finding suggests that later attentional processes were recruited more when someone with a diagnosis of schizophrenia looked happy, perhaps indicating that participants found this surprising.

Low Spatial Frequency Sensitivity and Emotional Face Processing in Adolescents: An Event-related Potential Study.

Slow maturation of visual pathways transmitting low spatial frequency (LSF) information may contribute to inaccurate facial emotion recognition in adolescence. We recorded ERPs from adolescents and adults to upright and inverted happy faces, fearful faces, and chairs, which were unfiltered, contained only LSFs, or only high spatial frequencies. P100s and N170s were larger for adolescents than adults, with the greatest effect size for LSF stimuli. For LSFs only, adolescents showed a larger N170 inversion effect for happy than for fearful faces, but adults showed the opposite response. Thus, immaturities in LSF pathways appear to impact facial expression processing in adolescents.

High-density electroencephalogram monitoring in the neonate.

Early diagnosis of neurologic conditions is crucial for successful early intervention; therefore, minimally invasive diagnostic procedures are invaluable during the neonatal period. The clinical usefulness of one such technique, the electroencephalogram (EEG), is well documented. However, the advent of high-density recording systems has extended its application. High-density EEG recording uses a significantly increased number of recordings sites: 128 to 256 electrodes compared with 10 to 30 in standard recording systems. This report describes the benefits of using more electrode sites and highlights the use of related procedures for the assessment of neural integrity across sensory modalities.

An Event-Related Potential Study of Social Information Processing in Adolescents.

Increased social awareness is a hallmark of adolescence. The primary aim of this event-related potential study was to investigate whether adolescents, in comparison to adults, would show relatively enhanced early neural processing of complex pictures containing socially-relevant information. A secondary aim was to investigate whether there are also gender and age differences in the ways adolescents and adults process social and nonsocial information. We recorded EEGs from 12-17 year-olds and 25-37 year-olds (N = 59) while they viewed pleasant pictures from the International Affective Picture System. We found age-related amplitude differences in the N1 and the LPP, and gender-related differences in the N2 region for socially-relevant stimuli. Social pictures (featuring mostly young children and adults) elicited larger N1s than nonsocial stimuli in adolescents, but not adults, whereas larger LPPs to social stimuli were seen in adults, but not adolescents. Furthermore, in general, males (regardless of age) showed larger N2s to nonsocial than to social images, but females did not. Our results imply that compared to adults, adolescents show relatively greater initial orientation toward social than toward nonsocial stimuli.

Emotional processing and psychopathic traits in male college students: An event-related potential study.

Emotional processing deficits are often considered a hallmark of psychopathy. However, there are relatively few studies that have investigated how the late positive potential (LPP) elicited by both positive and negative emotional stimuli is modulated by psychopathic traits, especially in undergraduates. Attentional deficits have also been posited to be associated with emotional blunting in psychopathy, consequently, results from previous studies may have been influenced by task demands. Therefore, we investigated the relationship between the neural correlates of emotional processing and psychopathic traits by measuring event-related potentials (ERPs) during a task with a relatively low cognitive load. A group of male undergraduates were classified as having either high or low levels of psychopathic traits according to their total scores on the Psychopathic Personality Inventory - Revised (PPI-R). A subgroup of these participants then passively viewed complex emotional and neutral images from the International Affective Picture System (IAPS) while their EEGs were recorded. As hypothesized, in general the late LPP elicited by emotional pictures was found to be significantly reduced for participants with high Total PPI-R scores relative to those with low scores, especially for pictures that were rated as less emotionally arousing. Our data suggest that male undergraduates with high, but subclinical levels of psychopathic traits did not maintain continued higher-order processing of affective information, especially when it was perceived to be less arousing in nature.

Priming by natural category membership in the left and right cerebral hemispheres.

The cerebral representation of category information was examined in a single word priming paradigm, during which the N400 component of the event-related potential (ERP) was recorded. The visual half-field paradigm was employed in order to selectively stimulate the two hemispheres. To investigate which aspects of category membership are relevant in producing priming, two types of related stimuli were presented. In one condition pairs of exemplars had a higher amount of feature overlap (e.g., MOSQUITO-FLEA) than in the other (e.g., SOFA-VASE). Significant priming was obtained only for stimuli in the high feature overlap condition and then only when these were presented to the left visual field (LVF)/right hemisphere (RH). This finding was interpreted within our recent model of semantic memory wherein the right hemisphere represents items on the basis of distributed individual features, whereas the left hemisphere (LH) represents semantic information locally, within a spreading activation system, where priming occurs exclusively through associative links. It was concluded that knowledge regarding category membership is maintained in the RH, on the basis of feature coding.

Evidence for a new conceptualization of semantic representation in the left and right cerebral hemispheres.

Two experiments are reported that examined qualitative differences in how semantic information is represented in the two hemispheres. In the first experiment, items that were associatively related but did not share semantic features or membership in semantic categories produced priming when delivered to the LH (RVF) but not to the RH (LVF). In the second experiment items that shared semantic features but were neither associates nor in the same category produced priming in the RH (LVF), but not in the LH (RVF). Together, the two experiments support the theory that, in the right hemisphere, semantic memories are represented within a distributed system, on the basis of semantic features, whereas, in the left hemisphere representations are, as in local models, relatively more holistic, and are connected via associative links.

Physiological evidence that a masked unrelated intervening item disrupts semantic priming: implications for theories of semantic representation and retrieval models of semantic priming.

Event-related potentials were recorded in a paradigm where an unrelated word was interposed between two related words. In one condition, the intervening item was masked and in another condition it was not. The N400 component indicated that priming of the related word was disrupted by the intervening item whether it was masked or not. The data are interpreted to be inconsistent with retrieval models of priming.

ERP correlates of malingered executive dysfunction.

Assessment of malingering has become an integral part of many neuropsychological evaluations, particularly in forensic settings. However, traditional malingering measures are known to be vulnerable to both manipulation and coaching. Consequently, recent research has attempted to identify physiological indices of cognitive functioning that are less susceptible to overt manipulation. While prior studies have explored the validity of physiological assessment of memory deficits, this study evaluates the effectiveness of a physiological measure of executive functioning. This study used EEG recording in conjunction with a three-stimulus oddball design to compare neural responses in simulated malingerers feigning cognitive deficits associated with traumatic brain injury (TBI) and controls. Specifically, the study explored the efficacy of an event-related potential (ERP) known as P3a, which is believed to be an index of frontal lobe executive processes, specifically the attentional orienting response. The results of this study demonstrated that simulated malingerers did not produce a P3a response that was significantly different from control participants. Furthermore, the P3a in simulated malingerers did not demonstrate any of the properties reported in prior studies with TBI patients. Not only were malingerers unable to produce a significant change in their basic orienting response, but the very process of attempting to employ additional strategies to appear impaired produced other physiological markers of deception. Therefore, the P3a component appeared to be unaffected by an individual's motivation or overt performance, which suggests that it may have potential for development as a physiological measure for differentiating between malingerers and those with genuine TBI.

Attentional capture by emotional faces in adolescence.

Poor decision making during adolescence occurs most frequently when situations are emotionally charged. However, relatively few studies have measured the development of cognitive control in response to emotional stimuli in this population. This study used both affective (emotional faces) and non-affective (letter) stimuli in two different flanker tasks to assess the ability to ignore task-irrelevant but distracting information, in 25 adults and 25 adolescents. On the non-emotional (letter) flanker task, the presence of incongruent flanking letters increased the number of errors, and also slowed participants' ability to identify a central letter. Adolescents committed more errors than adults, but there were no age-related differences for the reaction time interference effect in the letter condition. Post-hoc testing revealed that age-related differences on the task were driven by the younger adolescents (11-14 years); adults and older adolescents (15-17 years) were equally accurate in the letter condition. In contrast, on the emotional face flanker task, not only were adolescents less accurate than adults but they were also more distracted by task-irrelevant fearful faces as evidenced by greater reaction time interference effects. Our findings suggest that the ability to self-regulate in adolescents, as evidenced by the ability to suppress irrelevant information on a flanker task, is more difficult when stimuli are affective in nature. The ability to ignore irrelevant flankers appears to mature earlier for non-affective stimuli than for affective stimuli.

The feedback-related negativity (FRN) in adolescents.

This study examined age-related differences in the ERP correlates of external feedback processing (i.e., the feedback-related negativity [FRN]) in adolescent and young adult males, using a simple gambling task involving unpredictable monetary losses and gains of low and high magnitude. The FRN was larger after losses than gains, and was modulated by the magnitude of gains, but not the magnitude of losses, for all participants regardless of age. FRN amplitude was larger in adolescents than adults and also discriminated relatively less strongly between gains and losses in adolescents. In addition, the morphology of the waveform after high losses suggests that feedback in this condition may have been processed less efficiently by adolescents. Our results suggest that, although the FRN in adults and adolescents share some common characteristics, the neural processes that generate the FRN are still developing in midadolescence. These findings are discussed in the context of adolescent risk taking.

Expecting the unexpected: an N400 study of risky sentence processing in adolescents.

Teens often engage in risk taking. Avoiding risk may be aided by rapid access to cognitive models for danger. This study investigated whether these schemata are immature in adolescence. An N400 sentential priming paradigm compared risky, predictable, and incongruent sentence processing in adolescents and adults. Adults and teens processed predictable sentences similarly, as evidenced by equivalent N400 priming. However, in adults, more activation was required to access final words in a risky sentence than when the situation was predictable and benign. Conversely, teens showed little difference in N400s generated by risky or expected sentences. This suggests that risky scenario final words were unexpected for adults but not for adolescents because of age-related differences in world knowledge and risk-related schemata. This study may help to explain why teenagers engage in risky activities when there is little time for deliberative thought.

Frequency domain analyses of neonatal flash VEP.

A battery of frequency-dependent measures was made for high-density electroencephalographic recording measured in response to a flash stimulus in 12 normal term infants within 2 d of birth. Significant changes recorded in posterior electrodes in the same time window as the visual evoked potential (VEP) included increased local synchrony at approximately 40 Hz, increased power at approximately 16 Hz, the emergence of nonlinear coupling of lower (approximately 2 Hz) and higher frequency oscillations, and phase locking over a wide range of frequencies. This research provides evidence of neural synchrony and nonlinear coupling in response to a simple visual stimulus. These mechanisms are functional in early development. It is proposed that the frequency domain metrics of this study may augment current diagnostic measures of cortical function at birth.

Repetition and semantic priming of nonwords: implications for theories of N400 and word recognition.

ERPs were elicited by two types of orthographically legal, pronounceable nonwords. One nonword set was derived from and resembled real words, whereas the other set did not. Nonwords derived from related root words elicited N400 semantic priming effects similar to those obtained for words, indicating semantic activation of the root words. N400 repetition priming effects from nonderived nonwords were similar to those obtained for words. The elicitation of N400 by only derived nonwords would have suggested it was generated by the activation of word meanings, per se. However, both types of nonwords produced an N400, and an N400 priming effect. Because nonderived nonwords are not associated with meaning, the N400 cannot be generated by semantic activation per se. Rather, the N400 appears to be generated by orthographic/phonological analysis and is attenuated by the top-down feed of semantic information to the orthographic/phonological level.